U.S. patent application number 12/273073 was filed with the patent office on 2009-05-28 for method for producing toner.
This patent application is currently assigned to KAO CORPORATION. Invention is credited to Takeshi Ashizawa, Akihiro Eida.
Application Number | 20090136865 12/273073 |
Document ID | / |
Family ID | 40670019 |
Filed Date | 2009-05-28 |
United States Patent
Application |
20090136865 |
Kind Code |
A1 |
Eida; Akihiro ; et
al. |
May 28, 2009 |
METHOD FOR PRODUCING TONER
Abstract
A method for producing a toner, including at least the following
steps: step (A): pulverizing a negatively chargeable charge control
resin that does not soften at a temperature of 180.degree. C. or
lower to an average particle size of from 0.05 to 2 .mu.m; step
(B): melt-kneading at least a pulverized product of the negatively
chargeable charge control resin obtained in the step (A), a resin
binder, and a colorant; and step (C): pulverizing a melt-kneaded
product obtained in the step (B) and classifying the pulverized
product. The toner obtained according to the present invention is
suitably used in, for example, the development of a latent image
formed in electrophotography, electrostatic recording method,
electrostatic printing method or the like.
Inventors: |
Eida; Akihiro;
(Wakayama-shi, JP) ; Ashizawa; Takeshi;
(Wakayama-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
KAO CORPORATION
Chuo-ku
JP
|
Family ID: |
40670019 |
Appl. No.: |
12/273073 |
Filed: |
November 18, 2008 |
Current U.S.
Class: |
430/137.19 ;
430/137.2 |
Current CPC
Class: |
G03G 9/0817 20130101;
G03G 9/08755 20130101; G03G 9/08746 20130101; G03G 9/08748
20130101; G03G 9/0975 20130101; G03G 9/081 20130101; G03G 9/08744
20130101; G03G 9/09733 20130101 |
Class at
Publication: |
430/137.19 ;
430/137.2 |
International
Class: |
G03G 9/087 20060101
G03G009/087 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 26, 2007 |
JP |
2007-303926 |
Claims
1. A method for producing a toner, comprising at least the
following steps (A) to (C): step (A): pulverizing a negatively
chargeable charge control resin that does not soften at a
temperature of 180.degree. C. or lower to an average particle size
of from 0.05 to 2 .mu.m; step (B): melt-kneading at least a
pulverized product of the negatively chargeable charge control
resin obtained in the step (A), a resin binder, and a colorant; and
step (C): pulverizing a melt-kneaded product obtained in the step
(B) and classifying the pulverized product.
2. The method according to claim 1, wherein the pulverizing of the
step (A) is a wet pulverization.
3. The method according to claim 1, wherein the negatively
chargeable charge control resin comprises a polycondensed product
obtained by polycondensation reaction of a phenol and an aldehyde,
wherein the phenol comprises a p-alkylphenol (a) having one
phenolic hydroxyl group and having no substituents at the
ortho-position of the phenolic hydroxyl group, and a bisphenol
compound (b) having two phenolic hydroxyl groups and having no
substituents at the ortho-position of each phenolic hydroxyl
group.
4. The method according to claim 3, wherein the bisphenol compound
(b) is contained in an amount of from 1 to 30% by mol of the
phenol, and wherein the aldehyde is at least one member selected
from the group consisting of paraformaldehyde and formaldehyde.
5. The method according to claim 3, wherein the p-alkylphenol (a)
is a compound represented by the following formula (i):
##STR00007## wherein each of X.sup.1 and X.sup.3 is independently a
hydrogen atom, a halogen, or an alkyl group having 1 to 3 carbon
atoms; and X.sup.2is an alkyl group having 1 to 12 carbon atoms,
and wherein the bisphenol compound (b) is a compound represented by
the following formula (ii): ##STR00008## wherein each of X.sup.4,
X.sup.5, X.sup.6 and X.sup.7 is independently a hydrogen atom, a
halogen, or an alkyl group having 1 to 3 carbon atoms; and X.sup.8
is an alkylene group having 1 to 5 carbon atoms.
6. The method according to claim 3, wherein a molar ratio of raw
materials for the polycondensation reaction of the phenol and the
aldehyde, i.e. the phenol/the aldehyde, is from 1/0.5 to 1/5.
7. The method according to claim 1, wherein the resin binder
comprises at least: a polyester (A) obtained by polycondensing an
alcohol component comprising an alkylene oxide adduct of bisphenol
A in an amount of from 90 to 100% by mol, and a carboxylic acid
component comprising an aromatic carboxylic acid compound in an
amount of from 75 to 100% by mol; and a polyester (B) obtained by
polycondensing an alcohol component comprising an
.alpha.,.omega.-linear alkanediol in an amount of from 90 to 100%
by mol and a carboxylic acid component comprising an aliphatic
dicarboxylic acid component in an amount of from 90 to 100% by mol,
wherein the polyester (B) is contained in an amount of from 3 to
40% by weight of the resin binder.
8. The method according to claim 7, wherein in the polyester (B),
the .alpha.,.omega.-linear alkanediol is 1,4-butanediol,
1,6-hexanediol, or a mixture thereof, and the aliphatic
dicarboxylic acid compound is fumaric acid.
9. The method according to claim 1, wherein the melt-kneading of
the step (B) is carried out in a temperature range between a
temperature calculated from a softening point of the resin binder
plus 10.degree. C. and a temperature calculated from a softening
point of the resin binder minus 10.degree. C.
10. A method for producing a toner, comprising at least the
following steps (B') and (C'): step (B'): melt-kneading a
negatively chargeable charge control resin that does not soften at
a temperature of 180.degree. C. or lower and has an average
particle size of from 0.05 to 2 .mu.m, a resin binder, and a
colorant; and step (C'): pulverizing a melt-kneaded product
obtained in the step (B') and classifying the pulverized
product.
11. The method according to claim 10, wherein the negatively
chargeable charge control resin comprises a polycondensed product
obtained by polycondensation reaction of a phenol and an aldehyde,
wherein the phenol comprises a p-alkylphenol (a) having one
phenolic hydroxyl group and having no substituents at the
ortho-position of the phenolic hydroxyl group, and a bisphenol
compound (b) having two phenolic hydroxyl groups and having no
substituents at the ortho-position of each phenolic hydroxyl
group.
12. The method according to claim 11, wherein the bisphenol
compound (b) is contained in an amount of from 1 to 30% by mol of
the phenol, and wherein the aldehyde is at least one member
selected from the group consisting of paraformaldehyde and
formaldehyde.
13. The method according to claim 11, wherein the p-alkylphenol (a)
is a compound represented by the following formula (i):
##STR00009## wherein each of X.sup.1 and X.sup.3 is independently a
hydrogen atom, a halogen, or an alkyl group having 1 to 3 carbon
atoms; and X.sup.2 is an alkyl group having 1 to 12 carbon atoms,
and wherein the bisphenol compound (b) is a compound represented by
the following formula (ii): ##STR00010## wherein each of X.sup.4,
X.sup.5, X.sup.6 and X.sup.7 is independently a hydrogen atom, a
halogen, or an alkyl group having 1 to 3 carbon atoms; and X.sup.8
is an alkylene group having 1 to 5 carbon atoms.
14. The method according to claim 11, wherein a molar ratio of raw
materials for the polycondensation reaction of the phenol and the
aldehyde, i.e. the phenol/the aldehyde, is from 1/0.5 to 1/5.
15. The method according to claim 10, wherein the resin binder
comprises at least: a polyester (A) obtained by polycondensing an
alcohol component comprising an alkylene oxide adduct of bisphenol
A in an amount of from 90 to 100% by mol, and a carboxylic acid
component comprising an aromatic carboxylic acid compound in an
amount of from 75 to 100% by mol; and a polyester (B) obtained by
polycondensing an alcohol component comprising an
.alpha.,.omega.-linear alkanediol in an amount of from 90 to 100%
by mol and a carboxylic acid component comprising an aliphatic
dicarboxylic acid component in an amount of from 90 to 100% by mol,
wherein the polyester (B) is contained in an amount of from 3 to
40% by weight of the resin binder.
16. The method according to claim 15, wherein in the polyester (B),
the .alpha.,.omega.-linear alkanediol is 1,4-butanediol,
1,6-hexanediol, or a mixture thereof, and the aliphatic
dicarboxylic acid compound is fumaric acid.
17. The method according to claim 10, wherein the melt-kneading of
the step (B') is carried out in a temperature range between a
temperature calculated from a softening point of the resin binder
plus 10.degree. C. and a temperature calculated from a softening
point of the resin binder minus 10.degree. C.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for producing a
toner, which is used in, for example, the development of a latent
image formed in electrophotography, electrostatic recording method,
electrostatic printing method or the like.
BACKGROUND OF THE INVENTION
[0002] Charge control resins have been used to give electric
charges to toners, among which the negatively chargeable charge
control resins which are colorless, white or pale-colored that are
applicable for color toners include copolymers of a sulfonate
group-containing acrylamide monomer and a vinyl monomer, a
polycondensed product obtained by polycondensation reaction of a
phenol and an aldehyde, and calixarene compounds, and the like.
However, a further improvement in triboelectric chargeability has
been desired for the toner in which the above-mentioned
polycondensed product is used.
[0003] On the other hand, for example, JP-A-2002-40717 discloses a
technique in which a charge control resin is present in the form of
fine particles having specified length and width, by controlling
the state of phase separation of the charge control resin using a
resin binder containing a specified amount of a tetrahydrofuran
(THF)-insoluble component, for the purposes of being free from
background fog in any of low-humidity environment to high-humidity
environment, showing excellent developability, and satisfying both
the low- temperature fixing ability and the high-temperature offset
resistance.
[0004] In addition, JP-A-2003-280266 discloses a toner containing
at least a colorant and a calixarene compound as a charge control
agent, obtained by dissolving a toner composition containing a
modified polyester resin capable of forming a urea bond as a resin
binder in an organic solvent, subjecting the solution to a
poly-addition reaction in an aqueous medium to give a dispersion,
removing the solvent of this dispersion, and washing the residue,
for the purpose of obtaining a toner in which a charge control
agent is homogeneously dispersed in the toner particles, thereby
giving a stable triboelectric chargeability over a long period of
time. Further, JP-A-2003-280266 discloses that a resin binder and a
charge control agent are previously kneaded, whereby giving a state
in which the resin binder and the charge control agent are
initially sufficiently adhered to each other, thereby providing a
state in which the dispersion is effectively carried out;
consequently, the charge control agent is excellently dispersed in
the resin binder, so that the dispersion diameter of the charge
control agent becomes small, thereby giving excellent triboelectric
properties, and that a resin binder, a charge control agent, and a
solvent are mixed with a blender such as a Henschel mixer, upon
previously kneading the resin binder and the charge control agent,
and the resulting mixture is kneaded at a temperature lower than a
melting temperature of the resin binder, with a kneader such as a
twin roller or triple roller kneader to give a sample.
[0005] On the other hand, as a technique of pulverizing a charge
control agent, JP-A-2006-154026 discloses a toner for electrostatic
development containing a fine quaternary ammonium salt compound
adjusted to a specified BET specific surface area by wet
pulverization, for the purpose of sufficiently having charge
control effects such as excellent triboelectric stability and
triboelectric retainability even with a small amount of use.
SUMMARY OF THE INVENTION
[0006] The present invention relates to: [0007] [1] a method for
producing a toner, including at least the following steps (A) to
(C): [0008] step (A): pulverizing a negatively chargeable charge
control resin that does not soften at a temperature of 180.degree.
C. or lower to an average particle size of from 0.05 to 2 .mu.m;
[0009] step (B): melt-kneading at least a pulverized product of the
negatively chargeable charge control resin obtained in the step
(A), a resin binder, and a colorant; and [0010] step (C):
pulverizing a melt-kneaded product obtained in the step (B) and
classifying the pulverized product; and [0011] [2] a method for
producing a toner, including at least the following steps (B') and
(C'): [0012] step (B'): melt-kneading a negatively chargeable
charge control resin that does not soften at a temperature of
180.degree. C. or lower and has an average particle size of from
0.05 to 2 .mu.m, a resin binder, and a colorant; and [0013] step
(C'): pulverizing a melt-kneaded product obtained in the step (B')
and classifying the pulverized product.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The present invention relates to a method for producing a
toner having excellent triboelectric chargeability and
high-temperature offset resistance in a pulverized toner containing
a negatively chargeable charge control resin.
[0015] According to the method for producing a toner of the present
invention, a toner having excellent triboelectric chargeability and
high-temperature offset resistance in a pulverized toner containing
a negatively chargeable charge control resin can be obtained.
[0016] These and other advantages of the present invention will be
apparent from the following description.
[0017] In JP-A-2002-40717, a vinyl-based polymer has been used as a
charge control resin. This charge control resin, in general, has a
softening temperature of 180.degree. C. or lower, and the charge
control resin can be dispersed in the resin binder by kneading.
However, it would be difficult to disperse a charge control resin
that does not soften at 180.degree. C. by kneading with the resin.
JP-A-2003-280266 describes that the dispersion diameter can be made
smaller by kneading a calixarene compound together with a resin
binder; however, the publication does not disclose that the
calixarene compound itself is pulverized to a smaller particle
size. In addition, a toner disclosed in JP-A-2003-280266 is
produced by kneading a solution of the resin binder and a
calixarene compound together with a solvent, dissolving the
components in the solvent, subjecting the solution to a
poly-addition reaction in an aqueous solvent, and removing the
solvent, and this toner is not a toner obtained by pulverization
method. In order to make the dispersion diameter smaller according
to the pulverization method, a method of strongly kneading a
negatively chargeable charge control resin and a resin binder in
the melt-kneading with the resin binder is employed; however,
according to this method, it has been found that there arises some
disadvantages in the high-temperature offset resistance. In the
kneading of the resin binder and the calixarene compound of
JP-A-2003-280266, a solvent is used together, and a resin before
the poly-addition reaction is used, so that the kneading is not
strongly applied as in the pulverization method.
[0018] As a result of intensive studies for obtaining a toner
having excellent triboelectric chargeability and high-temperature
offset resistance in the pulverized toner containing a negatively
chargeable charge control resin, the present inventors have found
that in a method for producing a pulverized toner containing a
negatively chargeable charge control resin, as a means of
homogeneously dispersing the negatively chargeable charge control
resin in the resin binder, a toner having excellent triboelectric
chargeability and high-temperature offset resistance is obtained by
kneading a resin binder and a negatively chargeable charge
controlling resin of which particle size is made smaller by
previously pulverizing the resin, rather than strongly kneading the
negatively chargeable charge control resin and the resin binder to
improve dispersibility, and the present invention has been
perfected thereby.
[0019] The method for producing a toner of the present invention
includes the following steps: [0020] step (A): pulverizing a
negatively chargeable charge control resin that does not soften at
a temperature of 180.degree. C. or lower to an average particle
size of from 0.05 to 2 .mu.m; [0021] step (B): melt-kneading at
least a pulverized product of the negatively chargeable charge
control resin obtained in the step (A), a resin binder, and a
colorant; and [0022] step (C): pulverizing a melt-kneaded product
obtained in the step (B) and classifying the pulverized product,
and [0023] one of the features of the present invention resides in
that the negatively chargeable charge control resin pulverized in
the step (A) is melt-kneaded with the raw materials for the toner
containing a resin binder in the step (B). In the method for
producing a toner of the present invention, the dispersion of the
negatively chargeable charge control resin in the resin binder is
improved, so long as the negatively chargeable charge control resin
to be used in melt-kneading has an average particle size of from
0.05 to 2 .mu.m; therefore, in a case where a negatively chargeable
charge control resin that is unpulverized has an average particle
size within the above range, a pulverizing step of the negatively
chargeable charge control resin is not necessitated. Therefore, the
present invention also encompasses an embodiment that does not
include the step (A) in the above method, specifically, an
embodiment including the following steps: [0024] step (B'):
melt-kneading a negatively chargeable charge control resin that
does not soften at a temperature of 180.degree. C. or lower and has
an average particle size of from 0.05 to 2 .mu.m, a resin binder,
and a colorant; and step (C'): pulverizing a melt-kneaded product
obtained in the step (B') and classifying the pulverized
product.
[0025] As the negatively chargeable charge control resin, a
polyester resin, a phenolic resin or the like is used, among which
those that have excellent triboelectric chargeability do not in
many cases soften at 180.degree. C., which is a temperature higher
than the kneading temperature of the resin binder (usually at most
150.degree. C. or so). The negatively chargeable charge control
resin that does not soften at 180.degree. C. does not soften during
the melt-kneading with the resin binder, thereby giving poor
dispersibility in the resulting toner; therefore, the viscoelastic
properties of the resin binder during fixing of the toner are
inhibited, thereby making it likely to worsen the offset, and an
effect of improving triboelectric charges is likely to be smaller.
In view of the above, the dispersibility of the negatively
chargeable charge control resin has been tried to be improved by
adjusting the conditions for melt-kneading; however, simply
adjusting the conditions for melt-kneading not only does not give
sufficient dispersibility, but also leads to the deterioration of
the resin binder, thereby making likely to lower the
high-temperature offset. In the present invention, it is deduced
that the negatively chargeable charge control resin is previously
pulverized to a smaller particle size, or a negatively chargeable
charge control resin having a small particle size is used, thereby
providing an excellent dispersibility of the negatively chargeable
charge control resin, to give a toner capable of satisfying both
the triboelectric chargeability and the high-temperature offset
resistance without inhibiting the viscoelastic properties
inherently owned by the resin binder.
[0026] In the step(A), a negatively chargeable charge control resin
that does not soften to 180.degree. C. or lower is pulverized to an
average particle size of from 0.05 to 2 .mu.m, and in the step
(B'), a negatively chargeable charge control resin that does not
soften to 180.degree. C. or lower and has an average particle size
of from 0.05 to 2 .mu.m is used.
[0027] The negatively chargeable charge control resin that does not
soften to 180.degree. C. or lower in the present invention is not
limited in its softening point so long as the resin does not soften
at 180.degree. C. or lower, and a known one can be used. The resin
includes, for example, a polycondensed product (a phenolic resin)
obtained by polycondensation reaction of a phenol and an aldehyde,
a calixarene compound, and the like. Among them, the polycondensed
product obtained by polycondensation of a phenol and an aldehyde
and the calixarene compound are preferred, from the viewpoint of
triboelectric chargeability of the toner, and the polycondensed
product obtained by polycondensation of a phenol and an aldehyde is
more preferred, from the viewpoint of the temperature of
high-temperature offset generation of the toner. Here, the judgment
that the resin does not soften at 180.degree. C. or lower is
carried out according to the method described in Examples set forth
below.
[0028] The polycondensed product obtained by a polycondensation
reaction of a phenol and an aldehyde in the present invention is
not particularly limited, so long as the polycondensed product is
obtained by polycondensing the phenols and the aldehydes given
below.
[0029] As the phenol, a raw material containing a p-alkylphenol (a)
having one phenolic hydroxyl group and having no substituents at
the ortho-position, and a bisphenol compound (b) having two
phenolic hydroxyl groups and having no substituents at the
ortho-position of each hydroxyl group is used. Here, the phrase
"having no substituents" means that both of the carbon atoms
adjoining the carbon atom bound to a hydroxyl group is only bound
to a hydrogen atom except for being bound to other carbon atoms
forming an aromatic ring together with the carbon bound to a
hydroxyl group. By the polycondensation reaction of a phenol and an
aldehyde, the aldehyde is added to the carbon adjoining the
phenolic hydroxyl group of the phenol, whereby presumably forming a
polycondensed product in which the phenol and the aldehyde are
alternately connected to each other. This polycondensed product has
a structure in which a phenol having excellent charge retention is
connected, so that it is deduced that excellent triboelectric
chargeability is obtained.
[0030] It is preferable that the p-alkylphenol (a) includes a
p-alkylphenol represented by the formula (i):
##STR00001##
wherein each of X.sup.1 and X.sup.3 is independently a hydrogen
atom, a halogen, or an alkyl group having 1 to 3 carbon atoms; and
X.sup.2 is an alkyl group having 1 to 12 carbon atoms, and
preferably from 4 to 8 carbon atoms.
[0031] The p-alkylphenol represented by the formula (i) includes
p-t-butylphenol, p-t-octylphenol, p-t-dodecylphenol, and the
like.
[0032] It is preferable that the bisphenol compound (b) includes a
bisphenol compound represented by the formula (ii):
##STR00002##
wherein each of X.sup.4, X.sup.5, X.sup.6 and X.sup.7 is
independently a hydrogen atom, a halogen, or an alkyl group having
1 to 3 carbon atoms; and X.sup.8 is an alkylene group having 1 to 5
carbon atoms, and preferably 3 carbon atoms.
[0033] The bisphenol compound represented by the formula (ii)
includes a bisphenol A such as 2,2-bis(4-hydroxyphenyl)propane.
[0034] It is preferable that as the aldehyde, at least one member
selected from the group consisting of paraformaldehyde and
formaldehyde is used.
[0035] The p-alkylphenol (a) is contained in an amount of
preferably from 70 to 99% by mol, and more preferably from 80 to
98% by mol, of the phenol moiety as a constituting unit of the
above-mentioned polycondensed product, from the viewpoint of
triboelectric chargeability of the toner.
[0036] The bisphenol compound (b) is contained in an amount of
preferably from 1 to 30% by mol, and more preferably from 2 to 20%
by mol, of the phenol moiety as a constituting unit of the
above-mentioned polycondensed product, from the viewpoint of
dispersibility of the resin binder.
[0037] The molar ratio of the p-alkylphenol (a) to the bisphenol
compound (b), i.e. a/b, in the phenol moiety as a constituting unit
of the above-mentioned polycondensed product, is preferably from
99/1 to 70/30, and more preferably from 98/2 to 80/20.
[0038] The molar ratio for the raw materials for the
polycondensation reaction of the phenol to the aldehyde, i.e. the
phenol/the aldehyde, is preferably from 1/0.5 to 1/5, and more
preferably from 1/1.0 to 1/2.
[0039] The polycondensation reaction method of a phenol and an
aldehyde includes, for example, a method including the steps of
adding a phenol and an aldehyde in an organic solvent such as
xylene, reacting the components at a temperature from 80.degree. C.
to a boiling point of the solvent for 3 to 20 hours in the presence
of a strongly basic compound such as a hydroxide of an alkali metal
or an alkaline earth metal, while distilling off water, and
recrystallizing from a poor solvent such as an alcohol; and a
method including the steps of vacuum-drying an organic solvent, and
thereafter washing the residue with an alcohol such as methanol,
ethanol, or isopropanol. As the strongly basic compound, sodium
hydroxide, rubidium hydroxide, potassium hydroxide or the like can
be preferably used.
[0040] The polycondensed product obtained by polycondensation
reaction of a phenol and an aldehyde is contained in an amount of
preferably from 0.1 to 5 parts by weight, and more preferably from
0.2 to 4 parts by weight, based on 100 parts by weight of the resin
binder.
[0041] The calixarene compound is preferably a compound represented
by the formula (I):
##STR00003##
wherein each of R.sup.1 and R.sup.5 is independently a hydrogen
atom, an alkyl group having 1 to 5 carbon atoms, or
--(CH.sub.2).sub.mCOOR.sup.9, wherein R.sup.9 is a hydrogen atom or
an alkyl group having 1 to 3 carbon atoms, and m is an integer of
from 1 to 3, each of R.sup.2, R.sup.3, R.sup.4, R.sup.6, R.sup.7,
and R.sup.8 is independently a hydrogen atom, a halogen atom, an
alkyl group, an alkoxy group, an acyl group, or a cycloalkyl group
each having 1 to 12 carbon atoms, an aryl group having 6 to 12
carbon atoms, a hydroxyl group, a carboxyl group, an amino group
which may be substituted with an alkyl group and/or an acyl group,
each having 1 to 12 carbon atoms, a nitro group, a sulfonate group,
a sulfonamide, a carbamoyl group, or a cyano group, x is an integer
of from 4 to 8, and y is an integer of from 0 to 4, wherein the sum
of x and y is from 4 to 8, and more preferably a compound
represented by the formula (Ia):
##STR00004##
wherein x is as defined above. As the compound represented by the
formula (Ia), it is preferable that the compound contains a
compound in which x is 8, and more preferably contains a mixture of
compounds in which x is from 6 to 8.
[0042] The amount of the calixarene compound formulated is
preferably from 0.1 to 3 parts by weight, and more preferably from
0.5 to 3 parts by weight, based on 100 parts by weight of the resin
binder.
[0043] The toner in the present invention may properly contain
other negatively chargeable charge control agent besides the
polycondensed product obtained by polycondensation reaction of a
phenol and an aldehyde and the calixarene compound, within the
range so as not to impair the effects of the present invention.
Other negatively chargeable charge control agents are not
particularly limited, so long as the agent does not soften at a
temperature of 180.degree. C. or lower. The polycondensed product
obtained by polycondensation reaction of a phenol and an aldehyde
and the calixarene compound are contained in a total amount of
preferably 50% by weight or more, and more preferably 80% by weight
or more, of the negatively chargeable charge control agent.
[0044] A method of pulverizing the negatively chargeable charge
control resin is not particularly limited, and wet pulverization
with a ball-mill, including the step of mixing a pulverizing means
such as balls and a product to be pulverized in a dispersion medium
by driving a vessel, medium agitation, or the like; or dry
pulverization using a jet mill in which a product to be pulverized
is bombarded with a jet stream by means of a fluidized bed jet
mill, a gas stream jet mill, or the like may be employed. The wet
pulverization is preferred from the viewpoint of making it less
likely to cause fusion of the negatively chargeable charge control
resin during the pulverization, and being more easily likely to
obtain particles having smaller particle sizes.
[0045] As the dispersion medium used in wet pulverization, besides
water, an alcohol solvent such as methanol, ethanol, or isopropanol
can be used alone or in a mixture of two or more kinds. The alcohol
solvent such as methanol, ethanol, or isopropanol is preferred, and
ethanol is more preferred, from the viewpoint of improving the
dispersibility of the negatively chargeable charge control
resin.
[0046] The concentration of the negatively chargeable charge
control resin in the slurry prepared using the above-mentioned
dispersion medium is preferably from 5 to 30% by weight, and more
preferably from 10 to 20% by weight.
[0047] The mixing temperature is not particularly limited. The
mixing temperature is preferably 5.degree. C. or higher, and more
preferably 10.degree. C. or higher, from the viewpoint of stability
of the slurry concentration. In addition, the mixing temperature is
preferably 40.degree. C. or lower, and more preferably 30.degree.
C. or lower, from the viewpoint of stability of the slurry
concentration. From these viewpoints, the mixing temperature is
preferably from 5.degree. to 40.degree. C., and more preferably
from 10.degree. to 30.degree. C. The mixing time is not
particularly limited. The mixing time is preferably 10 minutes or
longer, and more preferably 30 minutes or longer, from the
viewpoint of pulverizability of the negatively chargeable charge
control resin. In addition, the mixing time is preferably 180
minutes or shorter, and more preferably 120 minutes or shorter,
from the viewpoint of the productivity of the pulverized product of
the negatively chargeable charge control resin. Therefore, the
mixing time is preferably from 10 to 180 minutes, and more
preferably from 30 to 120 minutes, from the viewpoint of
pulverizability and productivity.
[0048] Here, in a case where the negatively chargeable charge
control resin is pulverized by wet pulverization, according to a
known method, a dispersion medium may be removed, or an aggregate
of the negatively chargeable charge control resin obtained by
removing the dispersion medium may be disintegrated with a mixer,
and removed by a classifier or the like.
[0049] The pulverized product of the negatively chargeable charge
control resin obtained in the step (A) has an average particle size
of 0.05 to 2 .mu.m, preferably from 0.05 to 1 .mu.m, and more
preferably from 0.1 to 0.5 .mu.m. In addition, the negatively
chargeable charge control resin used in the step (B') has an
average particle size of from 0.05 to 2 .mu.m, preferably from 0.05
to 1 .mu.m, and more preferably from 0.1 to 0.5 .mu.m. The average
particle size of the negatively chargeable charge control resin in
the present specification is measured according to the method
described in Examples set forth below.
[0050] Thus, the pulverized product of the negatively chargeable
charge control resin that does not soften at a temperature of
180.degree. C. or lower obtained in the step (A) is used in the
step (B), and the negatively chargeable charge control resin that
does not soften at a temperature of 180.degree. C. or lower and has
an average particle size of from 0.05 to 2 .mu.m is used in the
step (B').
[0051] In the step (B), at least the pulverized product of the
negatively chargeable charge control resin obtained in the step
(A), a resin binder, and a colorant are melt-kneaded, and in the
step (B'), at least the negatively chargeable charge control resin
that does not soften at a temperature of 180.degree. C. or lower
and has an average particle size of from 0.05 to 2 .mu.m, a resin
binder, and a colorant are melt-kneaded.
[0052] As the resin binder in the present invention, those resin
binders having a softening point lower than a softening point of
the negatively chargeable charge control resin are preferred, from
the viewpoint of exhibiting an effect in pulverization of the
negatively chargeable charge control resin.
[0053] The resin binder has a softening point of preferably from
110.degree. to 150.degree. C., and more preferably from 115.degree.
to 140.degree. C. In a case where two or more resins are used as a
resin binder, an average softening point obtained by taking a
weighed average is defined as a softening point of the resin
binder, and it is desired that the average softening point is
within the above-mentioned range. In addition, the resin binder has
a glass transition temperature of preferably from 50.degree. to
85.degree. C., and more preferably from 55.degree. to 80.degree. C.
The softening point and the glass transition temperature of the
resin binder are measured according to the methods described in
Examples set forth below.
[0054] The resin binder includes polyesters, vinyl resins, epoxy
resins, polycarbonates, polyurethanes, and the like. Among them,
the polyesters are preferred, from the viewpoint of offset
properties of the toner. The polyester is contained in an amount of
preferably 95% by weigh or more, more preferably 99% by weight or
more, and even more preferably substantially 100% by weight, of the
resin binder.
[0055] The polyester is obtained by polycondensing a known alcohol
component and a known carboxylic acid component, such as a
carboxylic acid, a carboxylic acid anhydride, or a carboxylic acid
ester.
[0056] It is preferable that the alcohol component contains an
alkylene oxide adduct of bisphenol A represented by the formula
(II):
##STR00005##
wherein RO is an oxyalkylene group, wherein R is an ethylene and/or
propylene group, a and b each shows the number of moles of the
alkylene oxide added, each being a positive number, and the sum of
a and b on average is preferably from 1 to 16, more preferably from
1 to 8, and even more preferably from 1.5 to 4, from the viewpoint
of triboelectric chargeability and high-temperature offset
resistance of the toner.
[0057] The alkylene oxide adduct of bisphenol A represented by the
formula (II) includes alkylene (2 or 3 carbon atoms) oxide (average
number of moles: 1 to 16) adducts of bisphenol A such as
polyoxypropylene-2,2-bis(4-hydroxyphenyl)propane and
polyoxyethylene-2,2-bis(4-hydroxyphenyl)propane, and the like.
[0058] The alcohol component other than the alkylene oxide adduct
of bisphenol A represented by the formula (II) includes ethylene
glycol, 1,2-propylene glycol, 1,4-butanediol, neopentyl glycol,
polyethylene glycol, polypropylene glycol, hydrogenated bisphenol
A, and the like.
[0059] The compound represented by the formula (II) is contained in
an amount of preferably 30% by mol or more, more preferably 50% by
mol or more, even more preferably 80% by mol or more, and even more
preferably substantially 100% by mol, of the alcohol component.
[0060] The carboxylic acid component includes aliphatic
dicarboxylic acids such as oxalic acid, malonic acid, maleic acid,
fumaric acid, citraconic acid, itaconic acid, glutaconic acid,
succinic acid, adipic acid, sebacic acid, azelaic acid,
n-dodecylsuccinic acid, and n-dodecenylsuccinic acid; aromatic
dicarboxylic acids such as phthalic acid, isophthalic acid, and
terephthalic acid; alicyclic dicarboxylic acids such as
cyclohexanedicarboxylic acid; tricarboxylic or higher
polycarboxylic acids such as trimellitic acid and pyromellitic
acid; acid anhydrides thereof, alkyl(1 to 3 carbon atoms) esters
thereof; and the like. The above-mentioned acids, acid anhydrides
and alkyl esters of the acids are collectively referred to herein
as carboxylic acid compound.
[0061] The alcohol component may properly contain a monohydric
alcohol, and the carboxylic acid component may properly contain a
monocarboxylic acid compound, from the viewpoint of adjusting the
molecular weight and improving the offset resistance of the
toner.
[0062] The polycondensation of the alcohol component and the
carboxylic acid component can be carried out, for example, at a
temperature of from 180.degree. to 250.degree. C. in an inert gas
atmosphere, and it is preferable that the polycondensation reaction
is carried out in the presence of an esterification catalyst, for
example, dibutyltin oxide, from the viewpoint of more remarkably
exhibiting the effects of the present invention.
[0063] The amount of the esterification catalyst that is present in
the reaction system is preferably from 0.05 to 1 part by weight,
and more preferably from 0.1 to 0.8 parts by weight, based on 100
parts by weight of a total amount of the alcohol component and the
carboxylic acid component.
[0064] Here, in the present invention, the polyester may be a
modified polyester to an extent that the properties thereof are not
substantially impaired. The modified polyester refers to, for
example, a polyester grafted or blocked with a phenol, a urethane,
an epoxy or the like according to the method described in
JP-A-Hei-11-133668, JP-A-Hei-10-239903, JP-A-Hei-8-20636, or the
like.
[0065] In the present invention, it is preferable that the
polyester contains at least two resins, from the viewpoint of the
fixing ability of the toner. Specifically, it is desired that the
polyester is a combination of a high-softening point polyester
having a softening point of preferably exceeding 140.degree. C. and
170.degree. C. or lower, more preferably from 150.degree. to
170.degree. C., and a low-softening point polyester having a
softening point of preferably from 90.degree. to 140.degree. C.,
and more preferably from 110.degree. to 140.degree. C. In addition,
the difference in the softening points between the high-softening
point polyester and the low-softening point polyester is preferably
from 20.degree. to 60.degree. C., and more preferably from
20.degree. to 40.degree. C., from the viewpoint of fixing ability
and storage property of the toner. Here, in a case where the
polyester contains three or more resins, it is preferable that two
kinds of resins of those contained in larger amounts satisfy the
above requirements. For example, in a case where the second and the
third largest amounts are of the same level, it is preferable that
the one contained in the largest amount and either one of the
second largest amounts satisfy the above requirements. In addition,
it is preferable that all of the polyesters have softening points
lower than that of the negatively chargeable charge control resin,
from the viewpoint of exhibiting an effect of the pulverization of
the negatively chargeable charge control resin in the present
invention.
[0066] The high-softening point polyester and the low-softening
point polyester has a weight ratio, i.e. high-softening point
polyester/low-softening point polyester, of preferably from 1/9 to
9/1, and more preferably from 2/8 to 8/2.
[0067] As the polyester in the present invention, those having an
average softening point of preferably from 110.degree. to
150.degree. C., and more preferably from 115.degree. to 140.degree.
C. The term "average softening point" as use herein refers to a
softening point of the polyester itself when one kind of the
polyester is used, or a weighed-average softening point when two or
more kinds of the polyesters are used, and the softening point of
each of the polyesters is measured according to the method
described in Examples set forth below. In addition, it is
preferable that the average softening point is lower than the
softening point of the negatively chargeable charge control resin,
from the viewpoint of exhibiting an effect of pulverization of the
negatively chargeable charge control resin in the present
invention.
[0068] The polyester has a glass transition temperature of
preferably from 50.degree. to 85.degree. C., and more preferably
from 55.degree. to 80.degree. C. The polyester has an acid value of
preferably from 0.5 to 40 mg KOH/g, and more preferably from 0.5 to
30 mg KOH/g, from the viewpoint of improving triboelectric
chargeability. The glass transition temperature and the acid value
of each of the polyesters as used herein are measured according to
the method described in Examples set forth below.
[0069] In addition, it is preferable that the resin binder in the
present invention contains at least a polyester having low
crystallinity (hereinafter referred to as "polyester (A)") and a
polyester having high crystallinity (hereinafter referred to as
"polyester (B)").
[0070] The crystallinity of the resin is expressed by a
crystallization index defined as a ratio of a softening point to a
highest temperature of endothermic peak determined with a
differential scanning calorimeter, i.e., softening point/highest
temperature of endothermic peak. Generally, when the
above-mentioned value exceeds 1.5, the resin is amorphous; and when
the value is less than 0.6, the resin is low in crystallinity and
mostly amorphous. The crystallinity of the resin can be adjusted by
the kinds of the raw material monomers and a ratio thereof,
production conditions (for example, reaction temperature, reaction
time, and cooling rate), and the like. In the present invention,
the term "polyester having high crystallinity" refers to a
polyester having a crystallization index of from 0.6 to 1.5, and
preferably from 0.8 to 1.2, and the term "polyester having low
crystallinity" refers to a resin having a crystallization index of
more than 1.5, or less than 0.6, and preferably more than 1.5.
Here, the highest temperature of endothermic peak refers to a
temperature of the peak on the highest temperature side among
endothermic peaks observed. When a difference between the highest
temperature of endothermic peak and the softening point is within
20.degree. C., the highest temperature of endothermic peak is
defined as a melting point. When the difference between the highest
temperature of endothermic peak and the softening point exceeds
20.degree. C., the peak is ascribed to a glass transition.
[0071] The polyester (A) having low crystallinity is obtained by
polycondensing an alcohol component containing an alkylene oxide
adduct of bisphenol A in an amount of 90 to 100% by mol, and
preferably from 95 to 100% by mol, and a carboxylic acid component
containing an aromatic carboxylic acid compound in an amount of 75
to 100% by mol, preferably from 85 to 100% by mol, and more
preferably from 90 to 100% by mol.
[0072] It is preferable that the alkylene oxide adduct of bisphenol
A contains an alkylene oxide adduct of bisphenol A represented by
the above-mentioned formula (II):
##STR00006##
wherein RO is an oxyalkylene group, wherein R is an ethylene and/or
propylene group, a and b each shows the number of moles of the
alkylene oxide added, each being a positive number, and the sum of
a and b on average is preferably from 1 to 16, more preferably from
1 to 8, and even more preferably from 1.5 to 4, from the viewpoint
of triboelectric chargeability and durability of the toner.
[0073] The alkylene oxide adduct of bisphenol A represented by the
formula (II) includes the same adducts as mentioned above,
including the alkylene (2 or 3 carbon atoms) oxide (average number
of moles: 1 to 16) adduct of bisphenol A such as
polyoxypropylene-2,2-bis(4-hydroxyphenyl)propane,
polyoxyethylene-2,2-bis(4-hydroxyphenyl)propane, and the like.
[0074] The alcohol component other than the alkylene oxide adduct
of bisphenol A represented by the formula (II) includes the same
components as mentioned above, including ethylene glycol,
1,2-propylene glycol, 1,4-butanediol, neopentyl glycol,
polyethylene glycol, polypropylene glycol, hydrogenated bisphenol
A, and the like.
[0075] The aromatic carboxylic acid compound includes aromatic
dicarboxylic acids such as phthalic acid, isophthalic acid, and
terephthalic acid; aromatic tricarboxylic or higher carboxylic acid
compounds such as 1,2,4-benzenetricarboxylic acid (trimellitic
acid), 2,5,7-naphthalenetricarboxylic acid, and pyromellitic acid;
carboxylic acid compounds such as acid anhydrides thereof, and
alkyl(1 to 3 carbon atoms) esters thereof; and the like. Among
them, terephthalic acid and isophthalic acid are preferable, and
terephthalic acid is more preferable, from the viewpoint of
environmental stability and durability of the toner. The carboxylic
acids, acid anhydrides thereof, and alkyl esters thereof are
collectively referred to herein as a carboxylic acid compound.
[0076] The carboxylic acid component other than the aromatic
carboxylic acid compound includes carboxylic acid compounds, such
as oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic
acid, itaconic acid, glutaconic acid, succinic acid, and adipic
acid, acid anhydrides of these acids, and alkyl(1 to 3 carbon
atoms) esters of these acids; and the like.
[0077] In the polyester (A), the alcohol component may properly
contain a monohydric alcohol, and the carboxylic acid component may
properly contain a monocarboxylic acid compound, from the viewpoint
of adjusting the molecular weight and improving the offset
resistance.
[0078] The polycondensation of the alcohol component and the
carboxylic acid component in the polyester (A) can be carried out,
for example, at a temperature of from 180.degree. to 250.degree. C.
in an inert gas atmosphere, and it is preferable that the
polycondensation reaction is carried out in the presence of an
esterification catalyst, for example, tin octylate, from the
viewpoint of more remarkably exhibiting the effects of the present
invention.
[0079] The amount of the esterification catalyst that is present in
the reaction system is preferably from 0.05 to 1 part by weight,
and more preferably from 0.1 to 0.8 parts by weight, based on 100
parts by weight of a total amount of the alcohol component and the
carboxylic acid component.
[0080] The polyester (A) has a softening point of preferably from
70.degree. to 140.degree. C., more preferably from 80.degree. to
140.degree. C., and even more preferably from 85.degree. to
135.degree. C., from the viewpoint of fixing ability of the toner.
The polyester (A) has a glass transition temperature of preferably
from 40.degree. to 70.degree. C., and more preferably from
55.degree. to 70.degree. C., and an acid value of preferably from 5
to 25 mgKOH/g, and more preferably from 5 to 15 mgKOH/g. The
softening point, the glass transition temperature, and the acid
value as used herein are measured according to the methods
described in Examples set forth below.
[0081] The polyester (B) having high crystallinity is obtained by
polycondensing an alcohol component containing an
.alpha.,.omega.-linear alkanediol in an amount of from 90 to 100%
by mol, and preferably from 95 to 100% by mol and a carboxylic acid
component containing an aliphatic dicarboxylic acid compound in an
amount of from 90 to 100% by mol, and preferably from 95 to 100% by
mol.
[0082] The .alpha.,.omega.-linear alkanediol includes ethylene
glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, and the like. Among them, 1,4-butenediol and
1,6-hexanediol are preferable.
[0083] The aliphatic dicarboxylic acid compound includes aliphatic
dicarboxylic acids such as oxalic acid, malonic acid, maleic acid,
fumaric acid, citraconic acid, itaconic acid, glutaconic acid,
succinic acid, adipic acid, sebacic acid, azelaic acid,
n-dodecylsuccinic acid, and n-dodecenylsuccinic acid; acid
anhydrides thereof, alkyl(1 to 3 carbon atoms) esters thereof; and
the like. Among them, fumaric acid is preferable. Here, the
aliphatic dicarboxylic acid compound refers to aliphatic
dicarboxylic acids, anhydrides thereof, and alkyl(1 to 3 carbon
atoms) ester thereof, as mentioned above. Among them, the aliphatic
dicarboxylic acids are preferable.
[0084] The molar ratio of the aliphatic dicarboxylic acid compound
to the .alpha.,.omega.-linear alkanediol in the polyester having
high crystallinity in the present invention, i.e., aliphatic
dicarboxylic acid compound/.alpha.,.omega.-linear alkanediol, is
preferably from 0.9 or more and less than 1.0, and more preferably
from 0.95 or more and less than 1.0, from the viewpoint of
production stability, and further from the viewpoint of being
capable of easily adjusting the molecular weight of the resin by
evaporation during a vacuum reaction in a case where the
.alpha.,.omega.-linear alkanediol is contained in a large
amount.
[0085] The polycondensation of the alcohol component and the
carboxylic acid component in the polyester (B) can be carried out
by reacting the components in an inert gas atmosphere at a
temperature of from 120.degree. to 230.degree. C., using an
esterification catalyst as occasion demands, a polymerization
inhibitor, and the like, or the like. Specifically, a method
including the step of charging an entire monomer in a single batch
in order to increase the strength of the resin, or alternatively a
method including the step of firstly reacting divalent monomers,
and thereafter adding and reacting trivalent or higher polyvalent
monomers in order to reduce low-molecular weight components, or the
like may be employed. In addition, the reaction may be accelerated
by reducing a pressure of the reaction system in the latter half of
the polymerization. Here, in order to obtain a polyester having
high crystallinity in the present invention, it is preferable that
the polyester is formed to have a larger molecular weight, and it
is more preferable that the reaction is carried out until the
viscosity of the reaction mixture becomes high. In order to obtain
a polyester having high crystallinity formed to have a larger
molecular weight, reaction conditions such as adjustment of the
molar ratio of the aliphatic dicarboxylic acid compound to the
.alpha.,.omega.-linear alkanediol as mentioned above, elevation of
the reaction temperature, increase in the amount of the catalyst,
and subjection to a dehydration reaction for a long period of time
under reduced pressure may be selected. Incidentally, a polyester
having high crystallinity formed to have a larger molecular weight
can be also produced by using a high output motor. However, when
the polyester is produced without particularly selecting production
equipment, a method including the step of reacting raw material
monomers together with a non-reactive low-viscosity resin and a
solvent is also an effective means.
[0086] The number-average molecular weight of the polyester (B) has
an adverse effect each on storage property of the toner when it is
too low, and on productivity of the toner when it is too high.
Therefore, the polyester has a number-average molecular weight of
preferably from 5,000 to 10,000, and more preferably from 6,000 to
9,000. The average molecular weight of the resin as used herein is
determined according to the methods described in Examples set forth
below.
[0087] In addition, it is preferable that the polyester (B)
contains high-molecular weight component in a certain amount, from
the viewpoint of durability of the toner; therefore, the polyester
(B) has a weight-average molecular weight of preferably from 40,000
to 100,000, and more preferably from 45,000 to 70,000.
[0088] The polyester (B) has a highest temperature of endothermic
peak of from 100.degree. to 140.degree. C., preferably from
100.degree. to 130.degree. C., and more preferably from 100.degree.
to 120.degree. C., from the viewpoint of fixing ability, storage
property and durability of the toner. The highest temperature of
endothermic peak as used herein is determined according to the
method described in Examples set forth below.
[0089] The polyester (B) has a melting point of preferably from
100.degree. to 140.degree. C., more preferably from 100.degree. to
130.degree. C., and even more preferably from 100.degree. to
120.degree. C., from the viewpoint of low-temperature fixing
ability of the toner. The melting point as used herein is
determined according to the method described in Examples set forth
below.
[0090] The polyester (A) is contained in an amount of preferably
from 60 to 97% by weight, more preferably from 65 to 95% by weight,
and even more preferably from 75 to 90% by weight, of the resin
binder, from the viewpoint of dispersibility of the negatively
chargeable charge control agent the polycondensed product obtained
by polycondensation reaction of the phenol and the aldehyde in the
resin binder.
[0091] The polyester (B) is contained in an amount of preferably
from 3 to 40% by weight, more preferably from 5 to 35% by weight,
and even more preferably from 10 to 25% by weight, of the resin
binder, from the viewpoint of dispersibility of the negatively
chargeable charge control agent the polycondensed product obtained
by polycondensation reaction of the phenol and the aldehyde in the
resin binder. When the polyester (B) is contained in an amount less
than 3% by weight, the storage modulus of the toner and the
triboelectric charge of the toner are likely to be lowered, and
when the polyester (B) is contained in an amount exceeding 40% by
weight, the triboelectric charge of the toner is likely to be
lowered.
[0092] The polyester (A) and the polyester (B) are contained in the
toner in a weight ratio, i.e. A/B, of preferably from 60/40 to
97/3, more preferably from 65/35 to 95/5, and even more preferably
from 75/25 to 90/10.
[0093] Here, in the present invention, the polyester (A) may be a
modified polyester to an extent that the properties thereof are not
substantially impaired. The modified polyester includes, for
example, a polyester grafted or blocked with a phenol, a urethane,
an epoxy or the like according to the method described in
JP-A-Hei-11-133668, JP-A-Hei-10-239903, JP-A-Hei-8-20636, or the
like, or a composite resin containing two or more kinds of resin
units including a polyester unit.
[0094] Besides the polyester (A) and the polyester (B), the toner
in the present invention may properly contain other resin binders
within the range so as not to impair the effects of the present
invention. The other resin binder includes resin binders besides
polyesters, including vinyl resins, epoxy resins, polycarbonates,
polyurethanes, and the like. The polyester (A) and the polyester
(B) are contained in a total amount, but not particularly limited
to, of preferably 95% by weight or more, and more preferably 99% by
weight or more, of the resin binder, from the viewpoint of
low-temperature fixing ability.
[0095] As the colorant, all of the dyes, pigments and the like
which are used as colorants for toners can be used, and carbon
blacks, Phthalocyanine Blue, Permanent Brown FG, Brilliant Fast
Scarlet, Pigment Green B, Rhodamine-B Base, Solvent Red 49, Solvent
Red 146, Solvent Blue 35, quinacridone, carmine 6B, isoindoline,
disazo yellow, or the like can be used. These colorants can be used
alone or in admixture of two or more kinds. The toner produced by
the present invention may be any of black toner, color toner, and
full-color toner. The colorant is contained in a total amount of
preferably from 1 to 40 parts by weight, and more preferably from 3
to 10 parts by weight, based on 100 parts by weight of the resin
binder.
[0096] In the present invention, besides the pulverized product of
the negatively chargeable charge control resin obtained in the step
(A), or the negatively chargeable charge control resin that does
not soften at a temperature of 180.degree. C. or lower and has an
average particle size of from 0.05 to 2 .mu.m, an additive such as
a releasing agent, a fluidity improver, an electric conductivity
modifier, an extender pigment, a reinforcing filler such as a
fibrous material, an antioxidant, an anti-aging agent, or a
cleanability improver may be further properly used as the raw
materials of the toner other than the resin binder and the
colorant.
[0097] The releasing agent includes waxes such as synthetic waxes
such as polypropylene wax, polyethylene wax, and Fischer-Tropsch
wax; coal waxes such as montan wax; petroleum waxes such as
paraffin waxes; and alcohol waxes. These waxes may be used alone or
in admixture of two or more kinds. The releasing agent is contained
in the toner an amount of preferably from 1 to 10 parts by weight,
more preferably from 2 to 10 parts by weight, and even more
preferably from 3 to 7 parts by weight, based on 100 parts by
weight of the resin binder.
[0098] In the melt-kneading, it is preferable that the raw
materials of the toner such as the resin binder and the colorant,
and further additives as occasion demands, besides the pulverized
product of the negatively chargeable charge control resin obtained
in the step (A), or the negatively chargeable charge control resin
that does not soften at a temperature of 180.degree. C. or lower
and has an average particle size of from 0.05 to 2 .mu.m are
homogenously mixed and thereafter treated with to a kneader. The
mixing of the raw materials of the toner may be either a method of
mixing all the raw materials such as the resin binder at one time
or a method of dividing the raw materials and mixing. As the
kneader, an open-roller type kneader, a twin-screw kneader, or the
like can be used, and the open-roller type kneader is preferred,
from the viewpoint of dispersibility of the negatively chargeable
charge control resin.
[0099] A mixer used for mixing the raw materials of the toner
includes a Henschel mixer, a Super mixer, and the like. A Henschel
mixer is preferred from the viewpoint of dispersibility.
[0100] In the melt-kneading of the raw materials of the toner, the
colorant and the negatively chargeable charge control resin can be
efficiently highly dispersed without repeating the kneading or
without a dispersion aid, by using a continuous open-roller type
kneader provided with feeding inlets and a discharging outlet for a
kneaded product arranged along an axial direction of the
roller.
[0101] The mixture of the raw materials of the toner may be fed to
the kneader from one feeding port and may be divided and fed to the
kneader from plural feeding ports. It is preferable that the raw
materials of the toner are fed to the kneader from one feeding
port, from the viewpoint of easiness of operation and
simplification of an apparatus.
[0102] The continuous open-roller type kneader refers to a kneader
of which melt-kneading member is an open type, and can easily
dissipate the kneading heat generated during the melt-kneading. In
addition, it is desired that the continuous open-roller type
kneader is a kneader provided with at least two rollers. The
continuous open-roller type kneader preferably used in the present
invention is a kneader provided with two rollers having different
peripheral speeds, in other words, two rollers of a high-rotation
roller having a high peripheral speed and a low-rotation roller
having a low peripheral speed. In the present invention, it is
desired that the high-rotation roller is a heat roller, and the
low-rotation roller is a cooling roller, from the viewpoint of
dispersibility of the raw materials of the toner.
[0103] The temperature of the roller can be adjusted by, for
example, a temperature of a heating medium passing through the
inner portion of the roller, and each roller may be divided in two
or more portions in the inner portion of the roller, each being
communicated with heating media of different temperatures.
[0104] In the present invention, it is preferable that the
temperature of the roller is set so that the melt-kneading is
carried out within the temperature range between a temperature
calculated from a softening point of the resin binder plus
10.degree. C. and a temperature calculated from a softening point
of the resin binder minus 10.degree. C., and more preferably a
temperature range between a temperature calculated from a softening
point of the resin binder plus 7.degree. C. and a temperature
calculated from a softening point of the resin binder minus
7.degree. C., from the viewpoint of dispersibility of the
negatively chargeable charge control resin. In a case where the
softening point of the resin binder is lower than the softening
point of the negatively chargeable charge control resin, it is also
preferable from the viewpoint that the kneading is carried out near
the softening point of the resin binder, whereby the negatively
chargeable charge control resin can be dispersed in the resin
binder without undergoing unification upon melting. Here, in a case
where the melt-kneading is carried out with a continuous
open-roller type kneader, the temperature of the melt-kneading
means a surface temperature of the kneaded product. The surface
temperature of the kneaded product can be measured with a
non-contact type laser thermometer or the like.
[0105] The temperature at the end part of the raw material
supplying side of the high-rotation roller is preferably from
100.degree. to 160.degree. C., and the temperature at the end part
of the raw material supplying side of the low-rotation roller is
preferably from 35.degree. to 100.degree. C.
[0106] In the high-rotation roller, the difference between a
setting temperature at the end part of the raw material supplying
side and a setting temperature at the end part of the kneaded
product discharging side is preferably from 20.degree. to
60.degree. C. , more preferably from 30.degree. to 50.degree. C.,
and even more preferably from 35.degree. to 45.degree. C., from the
viewpoint of preventing detachment of the kneaded product from the
roller. In the low-rotation roller, the difference between a
setting temperature at the end part of the raw material supplying
side and a setting temperature at the end part of the kneaded
product discharging side is preferably from 0.degree. to 50.degree.
C., more preferably from 0.degree. to 40.degree. C., and even more
preferably from 0.degree. to 30.degree. C., from the viewpoint of
kneading ability of the resin binder and the negatively chargeable
charge control resin.
[0107] The peripheral speed of the high-rotation roller is
preferably from 2 to 100 m/min. The peripheral speed of the
low-rotation is preferably from 1 to 90 m/min, more preferably from
2 to 60 m/min, and even more preferably from 2 to 50 m/min. In
addition, the ratio between the peripheral speeds of the two
rollers, i.e., low-rotation roller /high-rotation roller, is
preferably from 1/10 to 9/10, and more preferably from 3/10 to
8/10.
[0108] The two rollers may be arranged in parallel to each other,
and it is preferable that the two rollers are set so that the gap
between the rollers on the end part of the discharge side of the
kneaded product is wider than the gap between the roller at the end
part of the supplying side, from the viewpoint of even more easing
the kneading share, thereby preventing molecular cleavage or the
like of the resin. Specifically, the gap between the rollers at the
end part of the supplying side of the kneading product is
preferably from 0.05 to 2 mm, more preferably from 0.05 to 1 mm,
and even more preferably from 0.05 to 0.8 mm, and the gap between
the rollers at the end part of the discharge side is preferably
from 0.1 to 2 mm, more preferably from 0.3 to 1.5 mm, and even more
preferably from 0.5 to 1 mm.
[0109] Structures, size, materials and the like of the roller are
not particularly limited. Also, the surface of the roller may be
any of smooth, wavy, rugged, or other surfaces. In order to
increase kneading share, it is preferable that plural spiral
ditches are engraved on the surface of each roller.
[0110] Subsequently, the melt-kneaded product obtained in the step
(B) is subjected to a step (C), and the melt-kneaded product
obtained in the step (B') is subjected to a step (C'),
respectively.
[0111] The step (C) is a step of pulverizing a melt-kneaded product
obtained in the step (B) and classifying the pulverized product,
and the step (C') is a step of pulverizing a melt-kneaded product
obtained in the step (B') and classifying the pulverized
product.
[0112] It is preferable that the melt-kneaded product obtained in
the step (B) and/or the step (B') is pulverized after properly
cooling the melt-kneaded mixture to a pulverizable hardness before
the pulverization.
[0113] The pulverization of the melt-kneaded product may be carried
out at one time or in divided plural times. The pulverization
preferably includes rough pulverization and fine pulverization from
the viewpoint of pulverization efficiency and production
efficiency. It is preferable that the melt-kneaded product is
subjected to rough pulverization to a size such that the maximum
diameter is preferably 3 mm or less, and more preferably 2 mm or
less, and thereafter the resulting roughly pulverized product is
further subjected to fine pulverization by taking into
consideration a desired toner particle size. The phrase "the
maximum diameter of 3 mm or less" as used herein means that all of
the toner particles pass through a sieve having an opening of 3 mm.
Similarly, the phrase "the maximum diameter of 2 mm or less" as
used herein means that all of the toner particles pass through a
sieve having an opening of 2 mm.
[0114] As the pulverizer used in the subjection of the melt-kneaded
product to rough pulverization, Atomizer, Rotoplex, or the like can
be used.
[0115] The pulverizer used in the fine pulverization of the roughly
pulverized product includes a jet type pulverizer such as a
fluidized bed type jet mill and a gas stream type jet mill; a
mechanical pulverizer such as a turbo mill; and the like. In the
present invention, the jet type pulverizer is preferred from the
viewpoint of pulverizability.
[0116] The fluidized bed type jet mill used in the present
invention includes a pulverizer having the structure and principle
for finely pulverizing the particles, containing at least a
pulverization chamber arranged facing two or more jet nozzles in
its lower portion thereof, in which a fluidized bed is formed with
the particles fed into the pulverizing container by a high-speed
gas jet stream discharged from the jet nozzles wherein the
particles are finely pulverized by repeating the acceleration of
the particles and impact between the particles in the fluidized
bed.
[0117] In the jet mill having the above-mentioned structure, the
number of jet nozzles is not particularly limited. It is preferable
that two or more jet nozzles, and preferably from 3 to 4 jet
nozzles are arranged facing each other, from the viewpoint of
balance among volume of air, amount of flow and flow rate, impact
efficiency of the particles, and the like.
[0118] Further, a classifying rotor for capturing uplifted
particles having small particle sizes downsized by pulverization is
provided in an upper part of the pulverization chamber. The
particle size distribution can be easily adjusted by a rotational
speed of the classifying rotor. The finely pulverized product
(classified powder obtained by cutting off its upper limit) can be
obtained by classifying the pulverized product with the classifying
rotor.
[0119] The classifying rotor may be arranged in any of longitudinal
direction and latitudinal direction against the vertical direction.
It is preferable that the classifying rotor is arranged in the
longitudinal direction, from the viewpoint of classifying
performance.
[0120] Specific examples of a fluidized bed type jet mill provided
with plural jet nozzles and further containing a classifying rotor
include pulverizers disclosed in JP-A-Showa-60-166547 and
JP-A-2002-35631.
[0121] The fluidized-bed jet mill which may be preferably used in
the present invention includes the "TFG" Series commercially
available from Hosokawa Micron Corporation, the "AFG" Series
commercially available from Hosokawa Micron Corporation, and the
like.
[0122] In addition, the gas stream type jet mill includes, for
example, an impact type jet mill containing a venturi nozzle and an
impact member arranged so as to face the venturi nozzle, and the
like.
[0123] The gas stream type jet mill which may be preferably used in
the present invention includes the "IDS" Series commercially
available from Nippon Pneumatic Mfg. Co., Ltd., and the like.
[0124] Subsequently, the finely pulverized product obtained above
is classified.
[0125] The classifier includes air classifiers, rotor type
classifiers, sieve classifiers, and the like. In the present
invention, it is preferable that the classifier contains a
classifying rotor containing a driving shaft arranged in a casing
as a central shaft thereof in a vertical direction, and a
stationary spiral guiding vane arranged to share the same central
shaft as the classifying rotor, wherein the stationary spiral
guiding vane is arranged in a classification zone on an outer
circumference of the classifying rotor with a given spacing to the
outer circumference of the classifying rotor, from the viewpoint of
ability of removing fine powders. Specific examples of the
classifier having the structure described above include a
classifier shown in FIG. 2 of JP-A-Hei-11-216425, a classifier
shown in FIG. 6 of JP2004-78063 A, commercially available
classifiers such as the "TSP" Series and the "TTSP" Series
commercially available from Hosokawa Micron Corporation, and the
like.
[0126] It is preferable that the classifier used in the present
invention is used in the classification of fine powder to remove
mainly fine powders, i.e. to cut off its lower limit. The fine
powders removed may be again subjected to the classifier because
the necessary portion of the fine powders is recaptured by
re-classification.
[0127] A toner is thus obtained through the above steps, and the
surface of the toner obtained may be subjected to a surface
treatment by externally adding fine inorganic particles of a
hydrophobic silica or fine resin particles. It is preferable that
the surface treatment is a method including the step of externally
adding an external additive such as a fluidity improver such as a
hydrophobic silica to a surface of the toner with a mixer such as a
Henschel mixer. As the external additive, known fine particles,
including fine inorganic particles, such as fine hydrophobic silica
particles, fine hydrophobic titanium oxide particles, fine alumina
particles, fine cerium oxide particles, and carbon black; and fine
polymer particles of polycarbonate, polymethyl methacrylate,
silicone resin, or the like can be used.
[0128] The toner obtained by the present invention has a
volume-median particle size (D.sub.50) of preferably from 3.0 to
9.0 .mu.m, more preferably from 4.0 to 9.0 .mu.m, even more
preferably from 4.0 to 7.0 .mu.m, and even more preferably from 5.0
to 7.0 .mu.m. The term "volume-median particle size (D.sub.50)" as
used herein refers to a particle size of which cumulative volume
frequency calculated on a volume percentage is 50% counted from the
smaller particle sizes, and measured according to the method
described in Examples set forth below.
[0129] In addition, since the toner obtained by the present
invention has excellent dispersibility of the negatively chargeable
charge control resin, the negatively chargeable charge control
resin in the toner has an average particle size of preferably from
0.05 to 1.0 .mu.m, more preferably from 0.05 to 0.5 .mu.m, and even
more preferably from 0.1 to 0.5 .mu.m. The average particle size of
the negatively chargeable charge control resin as used herein is
measured according to the method described in Examples set forth
below.
[0130] The toner obtained by the present invention can be used
without being limited in its development method, and any of toners
for monocomponent development and toners for two-component
development can be used. Since the toner obtained by the present
invention has excellent triboelectric chargeability, and the toner
is preferably used in the monocomponent development for which a
stress is strong.
EXAMPLES
[0131] The following examples further describe and demonstrate
embodiments of the present invention. The examples are given solely
for the purposes of illustration and are not to be construed as
limitations of the present invention.
[Softening Point of Resin]
[0132] The softening point refers to a temperature at which a half
the amount of the sample flows out when plotting a downward
movement of a plunger of a flow tester against temperature, as
measured by using a flow tester (CAPILLARY RHEOMETER "CFT-500D,"
commercially available from Shimadzu Corporation), in which a 1 g
sample is extruded through a nozzle having a diameter of 1 mm and a
length of 1 mm while heating the sample so as to raise the
temperature at a rate of 6.degree. C./min and applying a load of
1.96 MPa thereto with the plunger.
[Acid Value of Resin]
[0133] The acid value is determined by a method according to JIS
K0070 except that only the determination solvent is changed from a
mixed solvent of ethanol and ether as defined in JIS K0070 to a
mixed solvent of acetone and toluene (volume ratio of acetone :
toluene=1:1).
[Highest Temperature of Endothermic Peak and Glass Transition
Temperature of Resin]
[0134] The highest temperature of endothermic peak is determined
using a differential scanning calorimeter ("Q-100," commercially
available from TA Instruments, Japan), by cooling a sample from
room temperature to 0.degree. C. at a cooling rate of 10.degree.
C./min, allowing the cooled sample to stand for 1 minute, and
thereafter heating the sample at a rate of 50.degree. C./min. When
a difference between the highest temperature of endothermic peak
and the softening point is within 20.degree. C., a temperature of
an intersection of the extension of the baseline of equal to or
lower than the highest temperature of endothermic peak and the
tangential line showing the maximum inclination between the
kick-off of the peak and the top of the peak is read as a glass
transition temperature. When a difference between the highest
temperature of endothermic peak and the softening point exceeds
20.degree. C., a temperature of an intersection of the extension of
the baseline of equal to or lower than the temperature of a peak
observed at a temperature lower than the highest temperature of
endothermic peak and the tangential line showing the maximum
inclination between the kick-off of the peak and the top of the
peak is read as a glass transition temperature.
[Volume-Median Particle Size (D.sub.50) of Toner]
[0135] The term "volume-median particle size (D.sub.50)" of the
toner as used herein means a particle size of the toner, of which
cumulative volume frequency calculated on a volume percentage is
50% counted from the smaller particle sizes. Measuring Apparatus:
Coulter Multisizer II (commercially available from Beckman Coulter
K.K.) [0136] Aperture Diameter: 50 .mu.m [0137] Analyzing Software:
Coulter Multisizer AccuComp Ver. 1.19 (commercially available from
Beckman Coulter K.K.) [0138] Electrolytic Solution: "Isotone II"
(commercially available from Beckman Coulter K.K.) [0139]
Dispersion: "EMULGEN 109P" (commercially available from Kao
Corporation, polyoxyethylene lauryl ether, HLB: 13.6) is dissolved
in the above electrolytic solution so as to have a concentration of
5% by weight, to give a dispersion. [0140] Dispersion Conditions:
Ten milligrams of a test sample is added to 5 mL of the above
dispersion, and the resulting mixture is dispersed in an ultrasonic
disperser for 1 minute. Thereafter, 25 mL of the electrolytic
solution is added thereto, and the resulting mixture is dispersed
in the ultrasonic disperser for another 1 minute, to give a sample
dispersion. [0141] Measurement Conditions: The above sample
dispersion is adjusted so as to have a concentration at which the
particle sizes of 30,000 particles can be determined in 20 seconds
by adding 100 mL of the above electrolytic solution to the above
sample dispersion. Thereafter, the particle sizes of 30,000
particles are determined to obtain a volume-median particle size
(D.sub.50) from the particle size distribution.
[Triboelectric Charges of the Toner]
[0142] A specified amount of a developer is supplied in a cell
provided in the Q/M meter, and only toner is aspirated for 90
seconds through a sieve having a sieve opening of 32 .mu.m (made of
stainless steel, wire diameter: 0.035 mm). The voltage change
generated on the carrier at this time is monitored, and the value
of [Total Electric Charges (.mu.C) After 90 Seconds/Weight (g) of
Toner Aspirated] is calculated as the triboelectric charges
(.mu.C/g).
[Judgment That Negatively Chargeable Charge Control Resin Softens
at Temperature of 180.degree. C. or Lower]
[0143] The endothermic peaks attributable to the softening point
upon the determination by heating at a rate of 10.degree. C./minute
from 20.degree. to 200.degree. C. with a differential scanning
calorimeter are observed. If the peaks are not observed at a
temperature of 180.degree. C. or lower, it is judged that the
negatively chargeable charge control resin does not soften at a
temperature of 180.degree. C. or lower.
[Average Particle Size of Negatively Chargeable Charge Control
Resin]
[0144] The phrase "average particle size of the negatively
chargeable charge control resin" as used herein means a particle
size the negatively chargeable charge control resin of which
cumulative volume frequency calculated on a volume percentage is
50% counted from the smaller particle sizes. Measuring Apparatus:
Laser diffraction particle size analyzer "LA-920" (commercially
available from HORIBA, Ltd.) [0145] Dispersion: "EMULGEN 109P"
(commercially available from Kao Corporation, polyoxyethylene
lauryl ether, HLB: 13.6) is dissolved in ion-exchanged water so as
to have a concentration of 5% by weight, to give a dispersion.
[0146] Dispersion Conditions: Ten milligrams of a test sample is
added to 5 mL of the above dispersion, and the resulting mixture is
dispersed in an ultrasonic disperser for 1 minute, to give a sample
dispersion. [0147] Measurement Conditions: To the measurement cell
is added ion-exchanged water and then the above-mentioned sample
dispersion is added thereto. The particles are subjected to a
measurement at a concentration at which the absorbance is
appropriate, and an average particle size is obtained from the
particle size distribution. [Average Particle size of Negatively
Chargeable Charge Control Resin in the Toner]
[0148] The average particle size of the negatively chargeable
charge control resin in the toner refers to a number-average
particle size, which is obtained by the following method.
[0149] The cross section of the toner is observed with TEM
(transmission electron microscope) (commercially available from
JEOL Ltd., JEM2100) at a magnification of 5,000 folds. An average
of the length and the breadth of the negatively chargeable charge
control resin is defined as a particle size, and an average of
particle sizes of 100 particles is defined as a number-average
particle size. Here, among the parallel lines drawn so as to
contact the contour of each of the negatively chargeable charge
control resin on the cross section of the toner, the parallel lines
that form the maximum distance between the parallel lines are
defined as length, and the parallel lines that form the minimum
distance between the parallel lines that are defined as
breadth.
Resin Production Example 1
[0150] A 5-liter four-necked flask equipped with a nitrogen inlet
tube, a dehydration tube, a stirrer and a thermocouple was charged
with 3308 g (90 mol) of
polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane (BPA-PO), 341
g (10 mol) of polyoxyethylene(2.2)-2,2-bis(4-hydroxyphenyl)propane
(BPA-EO), 792 g of fumaric acid (65 mol, based on a total amount of
100 mol of BPA-PO and BPA-EO), 5 g of hydroquinone, and 10 g of
dibutyltin oxide (0.23 parts by weight, based on 100 parts by
weight of the total amount of the alcohol component and the
carboxylic acid component), and the mixture obtained was heated to
from 180.degree. to 210.degree. C. over 5 hours under nitrogen
atmosphere, and reacted, and further reacted at 8.3 kPa for 1 hour.
Thereafter, 480 g of trimellitic anhydride (23.8 mol, based on a
total amount of 100 mol of BPA-PO and BPA-EO) was supplied to the
mixture, the mixture was reacted at normal pressure (101.3 kPa) for
1 hour, and the mixture was then reacted at 8.3 kPa until a desired
softening point was attained, to give a resin composition. The
resulting resin had a softening point of 155.8.degree. C., a glass
transition temperature of 64.7.degree. C., an acid value of 33.2
mgKOH/g, a highest temperature of endothermic peak of 72.5.degree.
C., and a ratio of the softening point/the highest peak temperature
of 2.15. The resulting resin is referred to as a resin A.
Resin Production Example 2
[0151] A 5-liter four-necked flask equipped with a nitrogen inlet
tube, a dehydration tube, a stirrer and a thermocouple was charged
with 1286 g (35 mol) of
polyoxypropylene(2.2)-2,2-bis(4-hydroxyphenyl)propane (BPA-PO),
2218 g (65 mol) of
polyoxyethylene(2.2)-2,2-bis(4-hydroxyphenyl)propane (BPA-EO), 1603
g of terephthalic acid (92 mol, based on a total amount of 100 mol
of BPA-PO and BPA-EO), and 10 g of dibutyltin oxide (0.20 parts by
weight, based on 100 parts by weight of the total amount of the
alcohol component and the carboxylic acid component). The mixture
was reacted at 230.degree. C. under nitrogen atmosphere until a
reaction rate of 90% was attained, and the mixture obtained was
then reacted at 8.3 kPa until a desired softening point was
attained, to give a resin composition. The resulting resin had a
softening point of 111.4.degree. C., a glass transition temperature
of 68.5.degree. C., an acid value of 3.2 mgKOH/g, a highest
temperature of endothermic peak of 73.5.degree. C., and a ratio of
the softening point/the highest peak temperature of 1.52. The
resulting resin is referred to as a resin B. The reaction rate as
used herein means a value defined by a value calculated by [the
empirical amount of formed water (mol)]/[the theoretical amount of
formed water (mol)].times.100.
Resin Production Example 3
[0152] A 5-liter four-necked flask equipped with a nitrogen inlet
tube, a dehydration tube, a stirrer and a thermocouple was charged
with 2997 g (72 mol) of 1,4-butanediol, 1637 g (30 mol) of
1,6-hexanediol, 5365 g(100 mol) of fumaric acid, and 5.5 g of
t-butyl catechol (TBC) (0.06 parts by weight, based on 100 parts by
weight of the total amount of the alcohol component and the
carboxylic acid component), and the mixture was reacted at
160.degree. C. over 5 hours, and then heated to 200.degree. C. and
reacted for 1 hour. Further, the mixture was reacted at 8.3 kPa
until a desired molecular weight was attained, to give a resin
composition. The resulting resin had a softening point of
115.0.degree. C., a highest temperature of endothermic peak of
110.degree. C., and a ratio of the softening point/the highest peak
temperature of 1.05. The resulting resin is referred to as a resin
a.
Production Example 1 of Negatively Chargeable Charge Control
Agent
[0153] A reflux reaction was carried out in 300 mL of xylene, using
0.225 mol of p-t-butylphenol, 0.225 mol of p-t-octylphenol, 0.032
mol of 2,2-bis(4-hydroxyphenyl)propane, 18.5 g of paraformaldehyde
(0.6 mol in terms of formaldehyde), and 3 g of a 5N aqueous
potassium hydroxide solution while distilling off water at
120.degree. C. for 8 hours. The reaction mixture was recrystallized
from methanol, and filtered, the residue was further washed with
methanol, and the solid obtained was dried, to give a charge
control agent a. The resulting charge control agent a did not
soften at a temperature of 180.degree. C. or lower. Here, the
p-alkylphenol (a) and the bisphenol compound (b) are contained in
the phenol in amounts of 93% by mol and 7% by mol (a molar ratio
a/b of 93/7), respectively, and the molar ratio of the phenol to
the aldehyde is 1/1.2.
Examples 1 to 4 and Comparative Examples 1 to 4
[0154] Thirty parts by weight of the resin A, 70 parts by weight of
the resin B, 5.0 parts by weight of a releasing agent "HNP-9"
(commercially available from Nippon Seiro), 3.0 parts by weight of
"Pigment Yellow 185" (commercially available from BASF) and 2.0
parts by weight of "Pigment Yellow 74" (commercially available from
DAINICHISEIKA COLOR & CHEMICALS MFG. CO., LTD.) as colorants,
and 3.0 parts by weight of the negatively chargeable charge control
resin as shown in Table 1 were previously mixed with a Henschel
mixer. Thereafter, the mixture was melt-kneaded with a continuous
twin roller type kneader "Kneadex" (commercially available from
MITSUI MINING COMPANY, LIMITED) having an outer diameter of the
roller of 0.14 m and an effective roller length of 0.7 m under the
conditions as shown in Table 1, to give a kneaded mixture. The
pulverization conditions and the melt-kneading conditions of the
negatively chargeable charge control resin are as given below.
[Wet Pulverization of Negative Chargeable Charge Control Resin]
[0155] The wet pulverization was carried out with a wet pulverizer
"Ball-Mill SC100/32-ZZ" (commercially available from MITSUI MINING
COMPANY, LIMITED). Five-hundred grams of the negatively chargeable
charge control resin was dispersed in 2833 g of ethanol (15% by
weight), and mixed with 760 g of zirconia balls (diameter: 0.2
.mu.m) at a circulating flow rate of 3 L/min, 25.degree. C. for 120
minutes. The resulting pulverized product was dried in a bucket,
and the re-aggregated mass formed by drying was disintegrated with
a 10 L Henschel mixer (ST/A0 blades, 300 rotations/min, 1
minute).
[Dry Pulverization of Negative Chargeable Charge Control Resin]
[0156] The dry pulverization was carried out with "Jet Mill IDS-2"
(commercially available from Nippon Pneumatic Mfg. Co., Ltd.)." The
operating conditions were such that a pulverization pressure of 0.5
MPa, the impact plates were conical, and the pulverization feed was
2 kg/h.
[Melt-Kneading Conditions A]
[0157] The operating conditions were such that the gap between the
roller, i.e. clearance, at the end part of the supplying side of
the kneaded product was 0.2 mm, that a peripheral speed of a
high-rotation roller (front roller) was 33 m/min and a peripheral
speed of a low-rotation roller (back roller) was 22 m/min, that the
high-rotation roller had a temperature of at the supplying side of
raw materials of 130.degree. C. and a temperature at the
discharging side of the kneaded mixture of 100.degree. C., and that
the low-rotation roller had a temperature at the supplying side of
raw materials of 75.degree. C., and a temperature at the
discharging side of the kneaded mixture of 35.degree. C. In
addition, the raw material mixture had a feeding rate of 10
kg/hour, and an average residence time was about 10 minutes.
[Melt-Kneading Conditions B]
[0158] The operating conditions were such that the gap between the
roller, i.e. clearance, at the end part of the supplying side of
the kneaded product was 0.2 mm, that a peripheral speed of a
high-rotation roller (front roller) was 33 m/min and a peripheral
speed of a low-rotation roller (back roller) was 11 m/min, that the
high-rotation roller had a temperature of at the supplying side of
raw materials of 130.degree. C. and a temperature at the
discharging side of the kneaded mixture of 100.degree. C., and that
the low-rotation roller had a temperature at the supplying side of
raw materials of 75.degree. C., and a temperature at the
discharging side of the kneaded mixture of 35.degree. C. In
addition, the raw material mixture had a feeding rate of 10
kg/hour, and an average residence time was about 10 minutes.
[Melt-Kneading Conditions C]
[0159] The operating conditions were such that the gap between the
roller, i.e. clearance, at the end part of the supplying side of
the kneaded product was 0.1 mm, that a peripheral speed of a
high-rotation roller (front roller) was 33 m/min and a peripheral
speed of a low-rotation roller (back roller) was 11 m/min, that the
high-rotation roller had a temperature of at the supplying side of
raw materials of 130.degree. C. and a temperature at the
discharging side of the kneaded mixture of 100.degree. C., and that
the low-rotation roller had a temperature at the supplying side of
raw materials of 75.degree. C., and a temperature at the
discharging side of the kneaded mixture of 35.degree. C. In
addition, the raw material mixture had a feeding rate of 10
kg/hour, and an average residence time was about 10 minutes.
[0160] Next, the resulting melt-kneaded mixture was rolled with a
cooling roller to cool, the cooled mixture was then roughly
pulverized with an atomizer, and the resulting pulverized product
was finely pulverized with "AFG" (commercially available from
Hosokawa Micron Corporation). The resulting pulverized product was
subjected to classification with "TTSP" (commercially available
from Hosokawa Micron Corporation) by cutting off its lower limit,
to give each of the toners of Examples 1 to 4 and Comparative
Examples 1 to 4, each having a volume-medium particle size
(D.sub.50) of 5.5 .mu.m.
Test Example 1 [Background Fog]
[0161] Each toner of Examples and Comparative Examples was loaded
in a nonmagnetic monocomponent development device "Oki Microline
5400" (commercially available from Oki Data Corporation) equipped
with an organic photoconductor (OPC), and allowed to stand under
the environmental conditions of 25.degree. C. and 50% RH for 12
hours, blank sheets having a printing ratio of 0% were then printed
out. Thereafter, the toner remaining on the photoconductive drum
was transferred to a mending tape, and an image density difference
.DELTA.E with the reference was determined with a color-difference
meter "X-Rite" (commercially available from X-Rite) to evaluate the
background fog. As the reference, a mending tape without any
treatment was used. Here, if .DELTA.E is less than 2.0, the results
are excellent. The results are shown in Table 1.
Test Example 2 [High-Temperature Offset Resistance]
[0162] The toner of each of Examples and each of Comparative
Examples was loaded in a nonmagnetic monocomponent development
device "Oki Microline 5400" (commercially available from Oki Data
Corporation), and a solid patch of 3 cm.times.8 cm was printed on
Xerox L sheet (A4) with a 3 cm margin from the top of the length
direction with adjusting the amount of toner adhered to 0.45
mg/cm.sup.2, and the printout was taken out in an unfixed state, to
give L sheet printed with an unfixed image.
[0163] Next, the L sheet printed with an unfixed image was fixed
with an external fixing device, a modified fixing device of
"Microline 3050" (commercially available from Oki Data Corporation)
at a fixing speed of 100 mm/sec, while raising the fixing
temperature from 160.degree. to 190.degree. C. in an increment of
5.degree. C. Here, it was visually confirmed if any soils due to
high-temperature offset were generated in the circulating part of
the fixing roller, i.e. the lower part of the L sheet. The lowest
temperature at which the soils caused by the high-temperature
offset is confirmed is referred to as a temperature of
high-temperature offset generation. The higher the temperature of
high-temperature offset generation, the more favorable. The results
are shown in Table 1.
TABLE-US-00001 TABLE 1 Negatively Chargeable Charge Control Resin
Physical Properties of Toner Average Average Properties of Toner
Particle Size Particle Temperature of Before Melt- Size of Charge
Triboelectric High-Temperature Pulverization Melt-Kneading Kneading
Control Resin Charges Background Offset Generation Kind Conditions
(.mu.m) Conditions (.mu.m) (.mu.C/g) Fog (.degree. C.) Ex. 1 Charge
Control Dry 2.0 Conditions A 0.7 -58 0.7 185 Agent a Pulverization
Ex. 2 Charge Control Wet 0.5 Conditions A 0.4 -63 0.5 190< Agent
a Pulverization Ex. 3 Charge Control Wet 0.5 Conditions B 0.1 -65
0.4 190< Agent a Pulverization Comp. Charge Control -- 30
Conditions A 2.0 -40 1.8 160 Ex. 1 Agent a Comp. Charge Control --
30 Conditions B 0.9 -53 1.1 180 Ex. 2 Agent a Comp. Charge Control
-- 30 Conditions C 0.4 -60 0.6 170 Ex. 3 Agent a Ex. 4 Charge
Control Dry 0.2 Conditions A 0.1 -40 1.9 180 Agent b Pulverization
Comp. Charge Control -- 0.4 Conditions A 0.4 -35 2.2 170 Ex. 4
Agent b Note: Charge Control Agent b: a calixarene compound "F-21"
(a mixture of compounds represented by the formula (Ia), wherein x
is 6 to 8), commercially available from Orient Chemical Co., Ltd.,
that does not soften at a temperature of 180.degree. C. or
lower.
[0164] It can be seen that the toners of Examples 1 to 3 have high
triboelectric charges, reduced generation of background fog, and
excellent high-temperature offset resistance, as compared to those
of Comparative Example 1 to 3. In addition, despite the fact that
the kind of the charge control resin used and the average particle
size of the charge control resin in the toner are the same in the
toners of Example 2 and Comparative Example 3, since the toner of
Example 2 obtained by pulverization of the charge control resin has
reduced generation of background fog, and excellent
high-temperature offset resistance, it is suggested that a
pulverized product of the charge control resin having a more even
particle size is obtained by previously pulverizing only the charge
control resin, and the pulverized product is melt-kneaded with a
polyester, whereby suggesting that excellent dispersibility of the
charge control resin is obtained and further the affinity between
the charge control agent and the polyester is improved. It can be
seen from the comparison of the toner of Comparative Example 4 and
the toner of Example 4 that even when a calixarene compound is
used, the toner of Example 4 in which the charge control resin is
previously pulverized has reduced generation of background fog and
a high temperature of high-temperature offset generation, so that
the toner satisfies both the triboelectric chargeability and the
high-temperature offset resistance.
Examples 5 and 6
[0165] The same procedures as in Example 1 were carried out except
that the resins shown in Table 2 were used in amounts shown in
Table 2 in place of 30 parts by weight of Resin A and 70 parts by
weight of Resin B, to give toners of Examples 5 and 6. Here, the
melt-kneading was carried out under conditions shown in Table
2.
[0166] The following properties were evaluated for the toners
obtained in Examples 5 and 6 and the toner of Example 1 in
accordance with Test Examples 3 and 4 given hereinbelow. The
results are shown in Table 2.
Test Example 3 [Temperature of Low-Temperature Offset
Generation]
[0167] The toner of each of Examples was loaded in a nonmagnetic
monocomponent development device "Oki Microline 5400" (commercially
available from Oki Data Corporation), and an unfixed image (3
cm.times.8 cm) was obtained on Xerox L sheet (A4), with adjusting
the amount of toner adhered to 0.50 mg/cm.sup.2. The unfixed image
obtained was fixed with an external fixing device, a modified
fixing device of "MicroLine 3050" (commercially available from Oki
Data Corporation) at a fixing speed of 100 mm/sec, while raising
the temperature of the fixing roller from 130.degree. C. in an
increment of 5.degree. C. The highest temperature at which the
soils on paper surface caused by the offset on low- temperature
side are observed is referred to as a temperature of
low-temperature offset generation.
Test Example 4 [Solid Image Quality]
[0168] The toner of each of Examples was loaded in a nonmagnetic
monocomponent development device "Oki Microline 5400" (commercially
available from Oki Data Corporation), and allowed to stand under
environmental conditions of 25.degree. C./50% RH for 12 hours, and
an image having a printing ratio of 100% was printed for 100
sheets. Of the images obtained, a 10th image, a 50th image, and a
100th image were visually observed, and the solid image quality was
evaluated in accordance with the following evaluation criteria.
[Evaluation Criteria for Solid Image Quality]
[0169] A: no blurs are generated up to a 100th sheet; [0170] B: no
blurs are generated up to a 50th sheet; and blurs are observed on
the 100th sheet; [0171] C: no blurs are generated up to a 10th
sheet; and blurs are observed on the 50th sheet; and [0172] D:
blurs are observed on the 10th sheet.
TABLE-US-00002 [0172] TABLE 2 Negatively Chargeable Charge Control
Resin Physical Properties of Toner Resin Binder Average Average
Properties of Toner Polyester Particle Size Particle Size
Temperature of (A) Polyester Before Melt- of Charge Triboelectric
Low-Temperature Solid Resin (B) Pulverization Melt-Kneading
Kneading Control Resin Charges Offset Generation Image A Resin B
Resin a Kind Conditions (.mu.m) Conditions (.mu.m) (.mu.C/g)
(.degree. C.) Quality Ex. 1 30 70 -- Charge Dry 2.0 Conditions A
0.7 -58 165 D Control Pulverization Agent a Ex. 5 10 70 20 Charge
Dry 2.0 Conditions A 0.4 -64 145 A Control Pulverization Agent a
Ex. 6 25 70 5 Charge Dry 2.0 Conditions A 0.6 -62 155 C Control
Pulverization Agent a Note) The amount of the resin binder used is
expressed by parts by weight.
[0173] It can be seen from the results of Table 2 that the toners
of Examples 5 and 6 have high triboelectric charges, low
temperatures of low-temperature offset generation and excellent
solid image quality, as compared to those of the toner of Example
1. From the above, it is presumed that the triboelectric
chargeability is more improved by a synergistic effect of the resin
a having high crystallinity which is said to be disadvantage as a
resin binder in triboelectric chargeability and the negatively
chargeable charge control agent a. In addition, since the toner has
excellent triboelectric chargeability, the toners of Examples 5 and
6 presumably have an equivalent level or higher background fog than
that of Example 1.
[0174] The toner obtained according to the present invention is
suitably used in, for example, the development of a latent image
formed in electrophotography, electrostatic recording method,
electrostatic printing method or the like.
[0175] The present invention being thus described, it will be
obvious that the same may be varied in ways. Such variations are
not to be regarded as a departure from the spirit and scope of the
invention, and all such modifications as would be obvious to one
skilled in the art are intended to be included within the scope of
the following claims.
* * * * *